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Successful Propagation of Cedar Species from Seed

David Mattern

Hort 202

One rarely thinks of pine cones when they think of a
valuable source seed; however most conifers produce many viable seeds annually
(or biannually) in the form of cones. Most conifers can be propagated in
various ways but they are most easily propagated by seed. Just think, in each
pine cone used in those festive holiday wreaths is a treasure trove of seed!

General Information

Before I begin, keep in mind that the cones of all
conifers are the female reproductive part on a tree. A pine cone is not the
seed itself but more like a protective capsule containing many seeds. Each conifer
species produces its own unique cone. Over the centuries conifers have
developed this unique adaptation type of fruiting body to combat the elements
and predators. Jack pine (Pinus banksiana) for example produces pine cones that will not open to release
its seed until it is stimulated by intense heat, giving them the advantage of being
the first saplings to arise after a forest fire. This is just one of the many
unique adaptations conifers undertake by producing cones.

Propagation From Seed

Keep in mind not all your seeds will germinate so
start with more than you need. Worst case scenario more seeds will germinate
than you need, in that case a small sapling makes a great gift for any occasion
especially when you can say you grew it yourself!

Obtaining Seed

It is possible to buy seed from a store or catalog
however it may be hard to find. The seed will be reliable and the specific
cultivar, height, form, size, and color will be known.(Photo: 6)

The easiest way is by collecting seed from an
existing tree or one that grows in the wild. This is assuming you can reach the
cones themselves, Cedars can reach up to an average of 60 feet as Peter Thompson describes as "frustratingly inaccessible."

When you look for cones on the ground don’t get
discouraged if you don’t find any. Pine cones of Cedars will actually “explode”
when ripe, bursting in flakes onto the ground as a way of spreading seed. Seeds mature during autumn to early winter, a select few may germinate that first year however most will require a stratification period. It is
possible to harvest the cones before they reach full maturity and let
them fully ripen in a warm dry area, that is assuming you can reach them in the
tree!

-Some quick tips on storage

If you are not ready to germinate your seeds right
away the seeds can be stored for later use. when it comes to storing seed the
golden rule is always store in a cool dry place to avoid dessication and the possibility
that the seed will germinate on its own. Store the seeds in a small paper bag
and store in a cool dry place making sure no moisture will reach the seeds.

Seed Preparation

Cedar seeds are cold lovers. In other words they require a stratification period to germinate, at least for eight weeks or so. In colder climates the
easiest way to encourage the highest germination is to plant the
seeds in late fall, and store in a vented cold frame. The natural temperature
fluctuations through winter from the onset of spring will stimulate a higher
germination rate in your seeds.

What is Stratification?

When all seeds are ripe they are in a period of
dormancy in some way shape or form. This dormancy varies between seed type to
seed type, and require different conditions to break dormancy and germinate. In
the case of Cedars, stratification is required. Stratification is simply a
chilling period exposing seeds to cold temperatures which allows for chemical
processes to function correctly and break dormancy. This is a natural response (or
defense if you will) of trees insuring that the seed will germinate at the
desired time of year. Thus increasing the viability of the seed and the
healthier the young saplings will be to grow and produce seeds of their own.

-Alternatives to Overcome Dormancy

One alternative method I discovered to best overcome this adaptation
comes from Geoff Bryant in his book Plant
Propagation A to Z. First place the seeds in a container filled with
moistened seed starter potting soil (or any potting soil mix will do so long as
it has good aeration), cover the seed-and-soil filled container, and leave
somewhere in a fairly warm environment out of direct sunlight. Leave it for
three to four days to allow the seeds to take up water. After three to four
days move the container to the refrigerator (not the freezer) to stratify the
seeds. Ten weeks is about the average. Routinely shake the container to keep
the soil loose, and aerated. Keep an eye on the seeds, if they start to
germinate remove them immediately. If after several weeks the seeds do not
germinate repeat the period of chilling, as some seeds require a double
chilling requirement.

Keep in mind most fridges draw moisture from the inside
air, to avoid desiccation be sure to keep your seeds in a sealed container at
all times when in the fridge.

Container and Media Prep.

Growing from containers (in the case of cedars) is
easiest, this way the saplings can be later
moved to the desired location when ready. It is best to sow the seeds in large containers more
long than wide, to promote adequate straight and uncongested root systems.

A good seed soil mix should be light and airy. Any soilless medium can be used so long as is well
drained and provides adequate pore space. Vermiculite is a common medium to use
for starting most seeds; it can be used alone or mixed in with a soilless
media.

Seed Sowing

The optimal time to sow Cedar seeds is in the spring. This way the young plants have an entire season to grow before the onset of winter. keep in mind most Cedar species tend to be marginally hardy into zone 6, so be prepared to provide some form of protection on cold nights. (Photo: 7)

Sow the seed around 68oF. This is not a requirement but an average, anywhere between 59- 72 degrees will be sufficient. Cedar seeds need darkness to germinate. When
planting gently push the seeds into the soil and lightly cover. The number of seeds per container will depend on the size of the container, in general allow adequate space for each seed to grow without getting cramped.
Most people make the mistake of burying their seeds to deep, creating more of a
graveyard than a seed bed. The seeds only need to be lightly covered to about a
half inch. Cover the containers with a clear plastic bag and store in a warm environment away from intense direct light. Germination will occur in about 14 - 42+ days. Once the seeds start to germinate the bag can be removed and if all threats of freezing are over, the containers of newly germinated saplings can be moved outside in a protected area (a small greenhouse works best). Make shure the plants have adequate water throughout the season. The use of fertilizers or other nutrient forms are generally not needed.

Post Care

The seedlings of Cedars (as with most conifers) will
grow slowly for the first two to three years, but don’t give up on them.

(Photo: 8)

Be sure to keep an eye on the saplings at least for the first 4 years or so, making sure they have adequate moisture available. Protect the saplings in winter to avoid freezing or other potential problems by covering the sapling, or protecting it from winds or snow build up. If the seeds were germinated indoors be cautious of transplant shock anytime you transplant or when moving the saplings outside. To better help them adjust, harden them off in a cold frame for several weeks first.

David Mattern

December 1, 2009

Hort 202

(Photo: 1)

Cedrus spp. CedarPine Family - Pinaceae

Cedrus
is the genus of true cedars though many are thought to be by their common names,
such as Eastern Red Cedar (Juniperus
virginiana) and White Cedar (Thuja
occidentalis). Native to Asia and Northern Africa, cedars are quick growing
(though slows with age) long lived trees reaching to about 60 to 120 feet in
height. Cones are large and showy, and actually hang upright on branches! These
trees work great in a large mass or as a specimen plant. One thing to note is
they tend to be marginally hardy above hardiness zone 6, so give them a little
protection from the cold and wind and the trees will thank you for it. Below
are examples of some Cedrus species
common in the nursery trade.

(Photo: 2)

Common Cedar species

(Photo: 3)

Blue Atlas Cedar, (Cedrus atlantica ‘Glauca’) named for its place of origin the Atlas
mountains in Northern Africa. slow growing reaching a height of 60 to 120 feet,
pyramidal in form as with most all conifers. Needles grown in small tufts along
branches.